Many printing and imaging systems utilize a print head to effect imaging on a final receiving medium. Ink-jet printing systems commonly utilize either direct printing or offset printing architecture. In a typical direct printing system ink is ejected from jets in the print head directly onto the final receiving medium. In an offset printing system, the print head jets the ink onto an intermediate transfer surface, such as a liquid layer on a drum. The final receiving medium is then brought into contact with the intermediate transfer surface and the ink image is transferred and fused or fixed to the medium.
In some direct and offset printing systems, the print head moves relative to the final receiving medium or the intermediate transfer surface in two dimensions as the print head jets are fired. Typically, the print head is translated along an X-axis while the final receiving medium/intermediate transfer surface is moved along a Y-axis. In this manner, the print head "scans" over the print medium and forms a dot-matrix image by selectively depositing ink drops at specific locations on the medium.
When moving or transporting a printing system that includes a print head, it is desirable to restrain or secure the print head to limit its motion. In this manner, the print head is protected from inadvertently contacting other internal components of the printer and possibly suffering damage or being jolted out of alignment should the printer experience a shock loading or other deleterious movement during transport. An exemplary mechanism for restraining a print head is found in the Phaser.RTM. 350 solid ink color printer manufactured by Tektronix, Inc. of Wilsonville, Oreg. This restraint mechanism comprises a first pin mounted on the end of a shaft that is axially aligned with a first boss on one side of the print head. To restrain the print head, the print head is tilted away from the printing position and is translated until a second boss on an opposite side of the print head engages a second, fixed pin within the printer. The operator then depresses a button on the side frame of the printer to translate the shaft and engage the first pin in the first boss on the print head.
As this mechanism fixedly positions the moveable shaft and pin within the X-axis travel path of the print head, it is most suitable for use with print heads that travel smaller distances along the X-axis during printing. In printers having a print head that translates greater distances along the X-axis, the above-described mechanism is less desirable. In these printers, the shaft and pin of this mechanism would need to be positioned a greater distance away from the print head to avoid interfering with print head travel during printing. This increases the width of the printer housing or requires the shaft to protrude from one end of the printer housing.
Thus, a need exists for a print head restraint system that is suitable for use with print heads that translate substantial distances during printing. The restraint mechanism should not interfere with normal printing operations and should be easy to actuate by an operator. The restraint mechanism should also include provisions that prevent its actuation during imaging and at all other times when actuation could result in damage to the print head.